The use of closure devices for covering microbiological vessels, such as flasks, has been a widely accepted and longly used practice in microbiology. Closures are used in order to prevent the contamination of microorganisms being cultured or stored within the flasks by airborne contaminates or particulate matter. Additionally, these closures have been used to prevent the escape of microorganisms being cultured or stored in the flasks from being released from the flasks where they can become airborne and become contaminates themselves.
It is, generally, an absolute necessity that microorganisms or cultures must be grown under sterile conditions. Depending on the type of microorganism being cultured, either aerobic or anaerobic, closures have been designed to accommodate the specific growth requirements for each of these types of microorganisms. For example, aerobic microorganisms are only able to live in the presence of oxygen whereas anaerobic microorganisms are capable of growing, and in some circumstances are unable to grow, in the presence of oxygen. Therefore, for anaerobic organisms a closure may be required which is capable of maintaining sterile conditions within the interior of the flask or vessel by preventing the introduction of contaminating microorganisms while at the same time preventing the entrance of oxygen into the container or vessel.
Another requirement for a microbiological vessel or flask closure is that while maintaining the sterility of the microorganisms or cultures being grown therein, the closure should provide free access into the container or flask to facilitate the addition or removal of contents from the vessel or flask, such as sterile removal of microbiological culture from the vessel or flask.
Historically, cotton or gauze was formed into a plug and was inserted into the opening of a container or flask. These cotton or gauze plugs serve the general purpose of preventing contamination of the container or flask while simultaneously permitting the free exchange of oxygen with the atmosphere. This type of closure has many deficiencies such as it can be difficult to resterilize the plug for subsequent use and after repeated usage, this type of plug tends to readily decompose.
Another type of similar closure is described in U.S. Pat. No. 3,326,401 to De Long. This closure is adapted to fit over the open end of a microorganism container. The closure further includes a disposable plug made from a porous material which is positioned within the closure. This device has the deficiency that it does not allow for a seal between the closure and the container or flask to be established.
Another more recent development in microbiological container or flask closures provides the advantage of a filtering device combined with a plug type closure. This closure is referred to as the Steri Plug (CTP Corp. Huntington, N.Y.). This device is constructed of multiple components including a stopper portion, a filter, and associated gaskets and retainers. Because of its complex design, this type of closure is expensive and cumbersome to use.
Therefore, it would be desirable to have a closure assembly for use with microbiological containers or flasks in which the closure assembly includes a filter membrane and a seal which allows for creating an air and fluid tight seal between the closure and the container or flask and in which the closure assembly can be produced in a one step process thereby eliminating the complexity and lowering the cost of assembly and manufacture and eliminating the deficiencies described above for prior art closure devices.